@tangrs Electric current flow comes from two means. One is actual electrons (or protons) that physically move through space. The other, much more subtle concept, is that electric current flow is due to changing electric fields. Look up Displacement Current

@Misunderstood on parasitic cap. It is from the metal surface of the pin ( it can go for a few mm inside the device on bigger chips) to all of the other circuit conductors that pass nearby. The electric field makes an air capacitor between the pin and other conductors. It is specific to the special cases I indicated. For example, that pin on this device we've been discussing would shut down DDR4 if it was used as a pass-through route. It doesn't do diddly to the 2A current that comes from the ground or power connections of this device.

I have seen some cases where NC actually was intended to say DNC. Reading the datasheet (RTFM as they say) you find whether it has no internal connection or is meant to say that it is a must-not-connect. I double check most everything. I have designed pacemakers, there is no room for "oh well I'm sure that it actually means ... "

Well ... No internal connection means that there are no silicon connections to that pin, thus it is great for not hurting the device to connect as you please. As for parasitics, there are electrons flowing onto the tiny capacitor that the pin creates to the rest of the world. That parasitic won't upset this application, but if this were high speed or super low current, then it would upset the electrons on the board trace.